1. Field of the Invention
This invention relates to storage systems, and more specifically to data lifecycle management in storage systems.
2. Description of the Related Art
Storage area networks (SAN) provide a solution for storing and retrieving mass amounts of data. A typical SAN network architecture may consist of one or more host devices interconnected to one or more network devices or switches through an interface. The network devices or switches may then be interconnected to one or more data storage devices through a second network or interface. Many SAN architectures use fiber channel (FC) as the interface or network, however, Ethernet, Infiniband, Internet, and other networks/interfaces may also be used in a SAN architecture.
In current storage networking systems, applications' data are consolidated to central storage systems via a storage network and managed centrally. For example, Hitachi Data System provides Lightning 9900V series as a high-end storage system. Applications' data are stored in storage systems. Brocade provides Silkworm Fibre Channel (FC) switch for creating storage networks. Servers and storage systems are connected via FC switches so applications running on the servers can store data to the storage systems via the network.
Data has its lifecycle. For example, when data is created by an application, the application uses the data frequently. After a time has passed, the data may not be accessed as much, and eventually the data is discarded. Data also has its value. Depending on applications, types of data, business requirements, etc., the value of data will change.
Based on the lifecycle of data, data must be stored in an appropriate storage system. If data is business critical, the data must be stored in the safest storage system and must be available anytime. If data is not so important, storing such data in an expensive storage system with overmuch data protection doesn't make sense.
Data may be moved based on the lifecycle of the data. Data can be moved from one storage system to another storage system when value of data has changed so that the data is stored in an appropriate storage system. Sometimes such data movement is called data migration or data archiving. However, data movement must be done without disrupting applications that are using the data.
A virtual tape system has disk drives for faster data access and multiple tape libraries for storing un-used data. The IBM, Virtual Tape Server Virtual tape server (VTS) is an example of virtual tape storage. A virtual tape system allows servers to read and write data in itself. It provides a tape library interface so servers see virtual tape system as if it were a real tape library. A virtual tape system moves data between disk drives and tape libraries based on the number of accesses to data within a specified time period. This data movement is hidden from servers so there is no interruption on server side. If data was not used frequently, data is moved from disk drives to tape. When data is accessed, data is moved from tape to disk drives. There is a hierarchy between disk drives and tapes. A controller of the virtual tape system manages the data movement. However, this approach is problematic because hierarchical storage management (HSM) such as this doesn't scale. Further, because all access to data must pass through the controller of the virtual tape system, the controller becomes a performance bottleneck, therefore, making it problematic for large-scale systems.
Another approach is HSM software that is installed on servers. SAM-FS is an example of HSM software. HSM software manages disk storage systems and tape libraries which are connected to a server. HSM software moves data between them. HSM software uses the number of data accesses within a specified time period as timing of data movement. All servers who want to access data managed by HSM must have HSM software. However, this approach is problematic because servers without HSM software can't access the data.